Abstract
We investigate crystal microstructure in crystal-rich pumice and lava samples (six eruptions in the Central Andes) using X-ray CT. Slopes in the CSDs, which are obtained for phenocrysts, are independent of crystallinity. Phenocryst fragmentation in lavas is limited; this is inconsistent with experimental and theoretical predictions that interaction between crystals in shear flow should result in extensive crystal breakage in crystal-rich magma. This disconnection between natural samples and theoretical studies can be explained by considering that the crystal framework may be collapsed by gas bubbles, resulting in the shear-reduction of crystal-rich magma.
